Clinical Presentation, Convalescence, and Relapse of Rocky Mountain Spotted Fever in Dogs Experimentally Infected via Tick Bite

Abstract

Rocky Mountain spotted fever (RMSF) is a tick-borne disease caused by R. rickettsii in North and South America. Domestic dogs are susceptible to infection and canine RMSF can be fatal without appropriate treatment. Although clinical signs of R. rickettsii infection in dogs have been described, published reports usually include descriptions of either advanced clinical cases or experimental infections caused by needle-inoculation of cultured pathogen rather than by tick bite. The natural progression of a tick-borne R. rickettsii infection has not been studied in sufficient detail. Here, we provide a detailed description of clinical, hematological, molecular, and serological dynamics of RMSF in domestic dogs from the day of experimental exposure to infected ticks through recovery. Presented data indicate that neither the height/duration of fever nor detection of rickettsial DNA in dogs' blood by PCR are good indicators for clinical prognosis. Only the apex and subsequent subsidence of neutrophilia seem to mark the beginning of recovery and allow predicting a favorable outcome in Rickettsia-infected dogs, even despite the continuing persistence of mucosal petechiae and skin rash. On the other hand the appropriate (doxycycline) antibiotic therapy of sufficient duration is crucial in prevention of RMSF relapses in dogs.

Vector competence of Amblyomma americanum (Acari: Ixodidae) for Rickettsia rickettsii

“…Throughout the study, the dogs were housed indoors – in a climate-controlled animal facility as described before (Levin et al, 2014a). Dogs were provided with water and a standard dry food diet (Laboratory Canine Diet 5006; Purina, Fairburn, GA, USA) ad libitum.…”

“…Throughout the 2-wk study period, the body temperature of each dog was measured every morning; and temperatures ≥ 39.5 °C were defined as febrile (Aiello and Moses, 2016). Ear skin biopsies 2 mm diameter were collected aseptically from the ear twice per week under general anesthesia for PCR as skin biopsies appear to be significantly more useful in detecting rickettsial infection than blood-PCR (Levin et al, 2016). At 14 days post infestation, dogs were treated with oral doxycycline as previously described (Levin et al, 2014a) and transferred to an unrelated study.…”

Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States

“…Tickborne rickettsial infection in dogs can range from inapparent to severe. RMSF in dogs manifests with fever, lethargy, decreased appetite, tremors, scleral injection, maculopapular rash on ears and exposed skin, and petechial lesions on mucous membranes (91)(92)(93). A veterinarian should be consulted when tickborne rickettsial disease is suspected in dogs or other animals (see Protecting Pets from Tick Bites).…”

Synanthropic Mammals as Potential Hosts of Tick-Borne Pathogens in Panama

“…rickettsia . These symptoms can include skin rash, petechial hemorrhage in eyes and mucosa, lethargy and paralysis [27, 42]. Alternatively, it is known that C .…”